Variable speed drive system



Julle4, 194 0 I w i). HOOVER 2,203,149

VARIABLE SPEED DRIVE SYSTEI File Feb. 1p1, 1935 `4 sheets-sheet 1 o o o Q5 ,6 /2 /7 /f l /0 l o] 7\ A l N l A 57 3 i 'zo /9 .'/a /z o I l 8 A TTORNEY June 4,1940.- v HOQVER 2,203,149

. v VARIABLE` SPEED DRIVE SYSTEM I 4 l Vamo Hoover /NVENTOR A TTORNEY June 4, 1940. v. Hoov-R VARIABLE SPEED DRIVEA SYSTEM Filed Feb, 11, 1935 4 sheets-sheet s Vamo Hoover IN VEA/TOR A TTORNE y BYv v. HOOQR v 2,203,149

VARIABLE SPEED DRIVE 'SYSTEM June4, 1949.

- y, Filed Feb. 11,|1935 4 sheets-sheet 4 fik/f Vamo Hoover /N VENo/ev 1j A TTORNEY Patented June 4, 1940 PATENT NoFFicE VARIABLE SPEED' nmvE SYSTEM Vaino Hoover, Los Angeles, Calif., assigner to U. S. Electrical Motors, Inc., a corporation of California Application February 11, 1935, serial No. 5,899 l 3 claims. (ci. 'i4-23am.

This invention relates to an adjustable spe'ed drive and more particularly lto an integral construction, incorporating an electric motor in driving relation vto a driving pulley structure, a 5 driven pulley structure in driving relation Ato a load driving shaft and a belt for l'transmitting power from the driving pulley structure to the ,driven pulley structure, at least one of the pulley structures having an adjustable effective pulley diameter whereby the variation of speed ratio is obtained.

Such an adjustable pulley structure may include a pair of pulley sections having opposed inclined faces forming a. seat for a wedge-shaped/ driving belt. In order to provide means for acl-,Jy justing the effective diameter of the pulley structure the sections are made relatively axially adjustable. In this way the inclined faces can be brought closer together causing the belt to be urged radially. outward to produce an increased effective diameter; or they can be separated causing the belt to contact with the inclined faces at a shorter radial distance to produce a decreased effective diameter.

In the particular form of the device to be described hereinafter the adjustable speed drive has one pulley structure having an adjustable effective pulley diameter and one pulley structure which 'may have a fixed effective diameter. The belt or power transmitting member employed has a substantially constant effective 'length This gives rise to the problem of adjusting a belt of constant length to pulleys of relatively variable effective diameter. When only ployed the belt may be maintained in active driving relation to the pulley structures by adjusting the center distance between the axesof the two pulley structures simultaneously with the ladjust- .ment of the adjustable diameter -pulley structure. Thus in Aconstructions employing one adjustable diameter pulley structure, and in which the center distance is variable, it is necessary to rovicle means whereby the center distance and the diameter of the adjustable pulley structure may be adjusted at the relative rates required by the pulley diameters and the b elt length. There is, however, no constant relation between the rate of change of the center distance and the rate of change of the diameter of the adjustable pulley structure, as the diameter of the adjustable pulley is not a simple function of the center distance but is also a function of the belt length and the diameter of the other pulley structure.

one adjustable diameter pulley structure isem- In the construction to be described hereinafter u this problem is solved by providing positive means for adjusting the center distance between the axes of the two pulley structures and resilient means flor adjusting the diameter ofthe adjustable pulley structure to the value required by the ad- 5 justed center distance.

One form of the adjustable pulley structure which might be employed in the adjustable speed drive consists of two conical pulley sections urged into contact with the belt by means of a spring, 10 one of the pulley sections being directly fastened to the motor shaft and the other of the pulley sections being urgedby the spring toward the fixed pulley section. When the diameter of the adjustable pulley structure is changed, the belt 16 is moved axially with respect to each of the Willey sections. Thus, if one of the pulley seclons is fastened to the motor shaft, it is neces- 'sary to move the entire motor structure in an axial direction if it is desired to maintain the belt 20 in alignment. The rate at which the motor and the pulley section attached to the motor shaft must be moved axially is directly proportional to the rate at which the diameter of the adjustable pulley structure is changed. This, however, does not bear a constant relation to the rate of' change of the center distance. Thus the rate at which the motor and the pulley section attached to the motor shaft should be moved axially is also the function of the pulley diameters and the adjusted value of the center distance. 'I'he condition of belt alignment can therefore-onlybe approximately satisfied in any given construction and a. different rate of axial adjustment is required of the pulley supporting structure for each belt lengthv and pair of pulley diameters.

It is an object of this invention to obvlate this difficulty by providing a resiliently adjusted pulley structure, in which each of the'pulley sections are axially adjustable with respect to the supporting shaft, and in which interlocking means are provided for moving the pulley sections by equal and opposite increments with respect to the driving belt.

.It is another object of this invention to provide anA adjustable speed drive having a variable center distance between the driving and driven pulleys, in which the same Ameans may be employed for adjusting the center distance irrespective of the vparticular pulley diameters andl belt 50 length.

It is still another object of this invention to provide an adjustable speed drive in which the adjustable pulley structure may be mounted directly on -a standard motor shaft, and which 5 thereby permits the use of a driving motor'of standard construction.

It is still another object of this invention to provide an adjustable pulley structure in'which thopposing pulley sections are adjusted by equal and opposite increments and in which the means for interlocking ythe axial adjustment of the pulley sections is required to transmit only the difference between the frictional forces opposing the axial movements of the pulley sections.

In many variable speed power applications the speed requiredby the driven machine is much less than that provided at the driving shaft of the motor. This reductionin Ispeed may `be obtained by employing reduction gearing between the driven pulley of the adjustable speed drive having an adjustable diameter pulley structure and the driven machine; or the driven pulley structure of the adjustable speed drive may be mounted directly on the driving shaft of the driven machine and the reduction in speed may be obtained by the useof appropriate diameters for the driving and driven pulleys.

In this invention oneof the pulley struetures may be mounted on the motor shaft and the other pulley structure may be mounted on the load 4driving shaft, which is in active driving relation 'to the driven load. The diameter of the driven pulley structure is thus directly determined by the diameter of the driving pulley structure and the reduction in. speed which is required between the driving electric motor Aand the load driving shaft. Thus where a large reduction in speed is required the diameter of the driven pulley structure is much greater than that ofthe driving pulley structure. Large diameter V type pulleys are expensive'to construct. Thus in constructions of this type it is advantageous to use a flat faced driven pulley if it visl possible.

However, unless'the beltis maintained in accu` rate alignment at all times, the-belt will notl stay on a dat faced driven pulley.

invention to provide an adjustable speed drive and in which the center distance between the driving and driven pulleys is variable, in which means are provided for .maintaining the belt in accurate alignment, whereby a fiat faced driven pulley of minimum width maybe employed.

. 'It is still another object o f this invention to provide an adjustable speed drive, in which means' are provided for compensating for belt .wear and elongation and in which-belt wear does not pro duce misallgnment of the driving belt.v

It is still another object of this invention to provide a multiple belt adjustable speed drive.'

in which the center distance between the drivhis.

ing and driven pulleys is variable and in which means are provided fo maintaining each ofthe belts in perfect alignment.

This invention possesses many other advantages and has other objects which may bev made more easily apparent from.a consideration of severalembodiments of the invention. For this purpose there are shown several forms in the .drawings accompanying. and forming a part of the present specication. These forms will now be described in detail which illustrate the general principles of the invention; butit is to be understood that this detailed description is not to be taken in a limiting sense since the Vscope of the invention is best dened' by the appended claims. a

Referring to the drawings:

Figure 1 is a plan view of an adjustable speed encarta drive embodying 'the invention. vThis view illusthe motor shaft `and the manner in which the I driven pulley structure may be mounted directly on the driving shaft of a driven machine.

Figure 2 is a plan view ofthe motor supporting structure of Figure 1 and illustrates in particular the means provided for movably supporting'the motor to vary the center distance between the driving'and driven pulley structures.k

-'Figure 3 is a side elevation of the motor supporting structure of Figure l,4 taken vfrom the front of Figure 1 and illustrates the means prof vided for guiding the movement of the supported` motor and' pulley structure,

Figure 4 is a detailed view of the adjustable pulley structure/of Figure l and illustrates the.

means provided for"interl o ckingly adjusting the axial positions of the pulley sections by equal and 1 .oppositeincrementa This view is partly in section. taken along the axis ofthe l Figurex is a sectional view of Athe adjustable pullylstructure of Figurefi taken along'the line I-L Figure 6 is a detailed view of the adjustable Apulley structure, taken from.' the top of 'Figure 4 and with a portion of/.thegprotectin'g housing removed.- V

Figure 7 illustrates another form of the adjust-v ablejspeed drive of Figures 1 to 3. In this form the driving motor` and adjustable pulley structure are pivotally supported .tavaryv the center dis-I motor shaft.`

tance between a driving and driven pulley struc- I tures.4 Figure is a detailed view of thepivotal support of Figure 7, taken from the left vhand `side of Figure 7. This view is partly in section, taken lalong the axis of theshaft forming the pivot.

' Figure 9 is a sectional view taken through the i gear housing of Figure 8 along the line 2 2.

Figure 10 is a plan view of another form of the adjustable speed drive, in which means are' pro-` vided for employing multiplegbelt pulleys.

Figure 1l is a detailed view of the multiple belt adjus able diameter pulley employed in the'con- ""struction of Figure 10. This view is partly in section, taken along Figure 12 is a sectional view, line-3-3of Figure 11.

Referring to Figure 1,

drive is formed by the driving electric motor I, which is in driving relation to thev adjustable pulley structure 2, `mounted on the motor shaft, vand which by meansof the belt g3 drives the pulley structure 4, mounted on the driving shaft 5 of the driven machine 6. The driven pulley 4 is illustrated fas a hat-faced pulley having 'a diameter considerably greater than that of the adjustable diameter driving pulley 2. However, it is to -be understood that a V-type pulley may be employed for the fixed diameter pulley if desired and that it particularly desirable to employ a V-type pull y for the xed diameter pulley, when the driving-and driven pulley structures are of the axis of the motor shaft.

taken along the the adjustable speed i comparatively equal diameter. The driving pui-- z able eective pulley diameters.V For instance,

it is desired to increase the effective diameter of 'the adjustable pulley structure, the pulley sections l and 8 are moved by equal increments toward the driving belt 3. This movement of the pulley sections toward each other forces the driving belt radially outward to define a larger effective diameter. Conversely a separating movement of the pulley sections allows the belt to move radially inward to define a smaller effective diameter. 'I'he pulley sections are constantly urged into driving relation with the belt by means of the spring 9. The means whereby the spring 9 adjusts the axial positions of the pulley sections will be described in connection with Figures 4 to 6.

It is obvious from the construction that as the diameter of the. adjustable pulley structure is increased, that the driving and driven pulleys must be moved toward each-other to provide the, center distance required by the belt length. Conversely when the diameter of the adjustable pulley structure is decreased the center distance betweenthe pulley structures musfbe increased. to adjust the belt to the decreased pulley diam-I eter. In the present instance the center distance between the driving and driven pulley structures is positively adjusted and the diameter of the adjustable pulley structure is resiliently adjusted by means of the spring 9 to the diameter required by the. adjusted center distance. To provide means for adjusting the center distance between the pulley structures the driving 'motor I 'is' mounted on the'sliding motor base III, which inA turn is supported by the sub-base II. The subbase II is provided with appropriate feet I2'for securing the motor supporting structure to the supporting foundation.

The movement of the sliding base III with respect to the sub-base II is guided by the tongue and groove construction formed by the engagement of the tongue members I3 and I4, Figure 3, formed on the sliding base, with the grooves I5 and I5 formed on the sub-base. One side of the groove I 6 is formed by the adjustable member I1, which provides means for adjusting the sliding clearance between the tongue members and the grooves. The adjustable member I1 is held in place by means of the bolts I8 Vwhich pass;

through appropriate slots formed in the mem-V ber I1 and which are threaded -into the sub-base. By means of the construction provided the move(- ment of the supported motor and adjustable pulley structure i's .so guided that the supporting shafts of the driving and driven pulleys are maintained paralleland the belt is maintained in alignment.

l The means provided for adjusting the position of the 4sliding base I 9 and the supported motor and pulley structure is illustrated by Figure 2. which is a plan view of the motor ysupportingV structure with the driving-motor removed. Referring to Figure 2: the position of the sliding base is adjusted by means of the lead screw I9, which threadedly engages the bushing 28, secured to the sliding base III and which is rotatably supported by means of the bushing 2l secured to the sub-base. The -axial position of the lead screw I9 is xed by means of the collars 22 and 23 which are suitably secured to the lead screw and which abut against the ends of the bushing 2|.

The vrotation of the lead screw may be suitably actuated by means of the handwheel 24 which is secured to the projecting end 25 of the lead screw. It is to be understood that the end 25 of the vlead screw 'which projects past bushing 2| may be extended to as great a distance as is desired, if it is desiredfvto adjust the speed ratio of the adjustable speed drive from a remote location. It

is obvious from the construction that the rotation of the handwheel 24 produces a corresponding adjustment of the center distance between the axes of the pulley ,structures and the resultant adjustment of the speed ratio. l l

The adjustable pulley structure 2 of Figure 1 is illustrated in detail by Figures 4 to 6.. Referring to Figure 4; the driving motor has the motor shaft 21 which projects from the motor frame 26 and which has supported thereon the shaft extension 28. 'I'he member 28 is suitably keyed to the motor shaft by the key 29 and is held against axial movement by the set screw 30. The pulley section 1 is provided with the axially extending hub 3|, which is slidably supported on the shaft extension 28. The pulley section 8 is provided with the hub 32, which by means `of the bushing 33 is slidably supported on the exterior surface 34 of the hub 3I. The bushing 33 maybe formed of a lubricant retaining bearing materialto reduce to a minimum the frictional force between the bushing. and the supporting surface v34. -In order to provide a construction having increased mechanical strength the bushing 33 is formed intwo parts located adjacentl to either end of the hun 32. Thus th'e central portion of the hub may be formed of a material having a greater mechanical strength than the bearinggmaterial 4forming'the bushing 33.

4The driving connection between the pulley sec.- tion 1 and the shaft extension 28 is formed by the key 35, Figure 5, which engages the member 1 28 and the hub 3l of the pulley section. The pulley section 8 is in turn rotated together with the pulley section 1 by the engagement of the key 36 with the hubsn32 and 3| of the pulley sections. f

The axial movement of the pulley sections is interlocked by means of the gears 31 and .3". which respectively-engagethe racks 39 and 40. forn'ied in the hub-3| of the pulley section 1. and the racks 4I and 42, formed in the hub 32 of the pulley section 8.- AThe gears 31 and 38 are rotatably supported in fixed axial position with' respect to the shaft extension 28 by the pin 43 which passes through the gears and the shaft extension. The gears 31 and 38 and the pin 43 are held in positionby the protecting housing 44 which telescopes over the hub of the pulleysection 8 and which is held in position by means'of the screws 45', as illustrated `by Figure 4. The

racks 39 and 40, formed in the hub 3|, are formed on one side of the gears and the racks 4I. aw! 42, formed in the hub 32, are formed on the other side of the gears. Thus as viewed in Figure 5,

the acks 39 and 48 are formed to the right of th ears and the racks' 4I and 42 are Vformed to the leftof the gears. The manner-'inwhich the engagement of the gears with the-racks, formed in the hub 3|. Thus if the pulley section a is moved toward the left the engagement of the rack 4I with the gear 31 causes the gear to rotate and the engagement of the gear 31 with rack 39 causes the rack 39 and the pulley section 1 to be moved 'an equal distance toward the right. Thus when one of the pulley sections is` moved in an axial direction the .other pulley section must .also move an equal distance in the opposite axial direction. Thus the pulley sections are at all times interlockingly adjusted by equal and opposite increments with respect to the driving belt. In order to insure that the load will be equally divided between the gears 31 and F8. both of the racks formed in the hub of a single pulley section may be formed in -perfect alignment by breaching both of the racks in the pulley hub at the same time.

The means whereby the spring 9 adjusts -the diameter of the pulley structure is best illustrated by Figure 4. One end of the spring -9v abuts against the shoulder 46 formed by the reverse side of the pulley section 8 and the other end of the spring abuts against the shoulder 41, formed on the removable cap 48. The cap 48 is provided with a threaded portion 49, which engages an internal thread formed in the end of the pulley hub 3|. The cap is threaded into the end of the pulley hub until the radialsurface 58,

formed on the cap, comes into contact with the end of hub 3|. The force exerted by the spring 8 on the cap serves effectively as a spring washer to lock the cap in position. It is obvious from the construction that the spring 9 urges the cap 48 and the pulley section 1 secured thereto toward the right and the pulley section 8 toward the left, as viewed in Figure 4. Thus the pulley sections 1 and 8 areconstantly urged into contact with the driving belt 3. As has been previously described, the structure associated with the gears 31 and 38 causesthe pulley sections tomove by equal and opposite increments with respect to the driving belt. Thus, when the diameter 'of pulley section 8 moves tothe position 8', to increase the effective diameter of thepulley structure without moving the belt in an axial direction.

The construction provided is also of particular utility in that the adjustable pulley structure 2 provides automaticmeans for compensating for belt wear or elongation; for if the belt wears or is increased in-length the spring 9 and gears 31 and 38 cause the pulley sections 1 and 8 to be moved toward the belt by equal increments, thus automatically maintaining the belt tension without producing any misalignment of the driving belt.

`It is to be noted that the axial force exerted by the adjusting spring 9 is directly transmitted to the pulley sections .1 and 8 and is not imposed on the gears, which interlock the axial adjust.

ment of the pulley sections. The gears 31 and 38 are required to transmit only the difference between the frictional forces between the bushing 33 and the-hub 3| and between the hub 3| and.

the shaft extension 28; for if v.there were no'frictional forces between the relatively slidable hubs, or if the frictional forces were exactly equal, then the pulley sections 1 and 8 would always be moved by equal and opposite increments by the spring 9, as the force exerted by the spring on both of tional forces between the relatively slidable pulley hubsl will never be exactly equal; thus one of the pulley sections will always tend to make the entire axial movement required to adjust the pulley diameter and the driving' belt will be thrown badly out of alignment. The interlocking means also provide means for maintaining the with respect to the motor shaft; for unless means are provided for fixing the position of the pulley sections with respect to the shaft extension 28 both of the pulley sections may move as a unit with respect to the motor shaft.

The construction provided is of particular utility'as the adjustable pulley structure may be completely assembled independent of themotor shaft. Thus the pulley structures may be kept in stock fully assembled, and may be shipped to any desired locality and assembled on a motor shaft as readily as any xed diameter pulley. rI'his cooperation of the pulley structure may be illustrated in connection with Figure 4. Referring to Figure 4: when the driving belt 3is removed from the pulley structure the pulley sections 1 and 8yare urged by the spring to their limiting maximum diameter position, thus giving access to the set'screw 30, which holds the pulley structure to the motor shaft. The entire pulley structure may thus be removed as a unit from the motor shaft by removing the set screw. Similarly, to mount the pulley structure on the motor shaft it is only necessary to set the key 29 in position and fasten the pulley structure to the motor shaft by means of the set screw 38.

Suitable means are provided for lubricating the relatively slidable surfaces of the pulley structure. In the present instance the removable cap 48 is provided with the lubricant conducting passage 5|, which is threaded to engage the pressure lubricating fixture-52. Thus lubricant vmay be injected throughvthe passage 5| into the lubricant retaining chamber-53, formed within the hub 3|. The centrifugal force created by the rotation of the pulley structure urges the lubricant from the lubricating chamber 53 to the supporting surfaces of the shaft extension 28 and the pulley hub 3| and to the supporting surfaces of the pulley section 8. The protecting housing 44 serves to prepair of lubricant retaining chambers for the gears 31 and 38.

Figures 7 te illustrate another form of an e adjustable speed -drive, in which the adjustable pulley structure of Figures 4 to 6 may be employed. In this form the driving motor is pivotally supported by the adjustable lbase 54, which is formed by the pivoting motor base '55 and the supporting base 56. The motor shaft has mounted thereon' the adjustable pulley structure 2, which by means of the belt 3 drives a driven pulley 51, mounted on the load driving shaft 58. The load driving shaft 58 may be rotatably supported by means 'of the supporting structure 59 and may be provided with suitable means for engaging a driven load., The supporting base 58 and the supporting structure 59 of the driven pulley may be supported on the base plate 60 to provide a common support for .the driving and driven pulley structures. The driven pulley 51 is illustrated as a V-type pulley and may be bf the type commonly `employed in fixed diameter V-belt drives.

'I'he speed ratio is adjusted by means of the handwheel 5| and the rotatably supported rod 82, which adjust the angular position of the pivoting'base 55 to vary the center distance between the driving and driven pulley structures. The means whereby the adjustment of the pivoting base is produced by the rotation of the rod 62 is illustrated in detail by Figures 8 and 9.

Referring to Figure-8; the pivoting base 55 is provided with the supporting arms 63 and 64 which are supported on the shaft 65 and keyed thereto by the key 66.. rThe shaft 65 isv in turn rotatably supported on the upright arms 61 and 68, formed on the supportingbase 56. The axial position of the shaft 65 is fixed by the contact of the collars 69 and 18 respectively with the arms 61 and' 68. Tliepivoting base 55 may be held in fixed axial position with respect to the shaft 65 by means ofthe set screws 13 and 14, which are respectively threaded into the arms 63 and 64 and which "secure the arms to the'shaft. The set screws 13 and 14 provide means for adjusting the axial position of the pivoting base 55 with the gear housing 15 is removably secured to the face 16 of the upright arm 61. 'I'he gear housing 15 encloses a worm which is rotated by the handwheel 6| and the rod 62 and which engages the worm wheel 11 mounted on the shaft 65. The worm wheel 11 may be suitably keyed to the shaft by the key 19. The housing 15 may vbe secured to the arm 61 by means of the bolts 88 which pass through the flange 8| formed on the housing and which are threaded into the arm 61. 'I'he gear housing may be provided with the removable cover 82, which gives access to the worm wheel 11 jand provides means whereby the worm wheel may be removed from the shaft 65 The construction of the gear housing is illustratedv in detail by Figure 9, which is a sectional view of the gear housing taken from thl ft hand side of Figure 8 along the line 2 2. Referring to Figure 9: the worm 83 is suitably coupled to the rod 62 by means of the coupling 84. The worm l83 is rotatably supported on the removable cover plates 85 and 86,'which provide means whereby the worm may be removed from the housing and which also provide means whereby the position of the Worm may be reversed withln the housing to vchange the position of the speed ratio adjusting handwheel to the opposite side of the gear housing. It is obvious from the construction that a rotation of the handwheel 6| produces a corresponding rotation of the wormwheel 11 and the resultant adjustment of the speed ratio 0f the adjustable speed drive. The angle of lead of the worm 83 may be made sufficiently small so that the worm eiectively locks the worm wheel 11 in the adjusted position. The

bolts 88, which hold the gear housing to the upright arm 61, are spaced at equal angular iriterv als so that the gear housing may be secured to the arm 61 in a plurality of angular positions to change the position of the speed ratio adjusting handwheel to the desired location.

driving motor and the adjustable pulley structure may be mounted in any desired relation with respect to the adjustable base and the speed ratio adjusting lhandwheel. Thus,v by reversing the position'of the worm in the gear housing and by To provide means for Bymeans of the construction provided the bushing |89.

' rotating the base 56, so that the arm 61 is on the right hand side, as viewed in Figure 8, the driving motor structure may be assembled so that the adjusting handwheel is at the right of the ad justable motor base, as viewed in Figure 8, and the motor may be mounted on the adjustable base so that the adjustable pulley structure is at the left of the base. It is also possible to mount -the driving motor so that both the adjustable 'p ulley structure and the speed ratio adjusting handwheel are on the same side -of the motor base.

A Figures 10 to 12 illustrate a form of the adjustable speed drive in which means are provided for employing multiple belt adjustable diameter pulleys. Referring to Figure 18: the adjustable speed drive is formed by the driving electric motor 81, which is in driving relation to the multiple belt adjustable diameter pulley 88 mounted on the motor shaft and which by means of the belts 89 and 98 drivesthe multiple belt pulley 9|, mounted on the load driving shaft 92. The load driving shaft-92 may be provided with suit. able bearing vsupports 93 and 94v and may be provided with a load driving extension 95 for engaging a driven load. The driven pulley 9| mayI be of the type commonly employed in multiple V-belt drives, however, the spacing and the width of the grooves for the belts must be determined from the dimensions of the adjustable diameter pulley 88.

As in the construction of Figures 1 to 3 the driving electric motor 81 is supported on the sliding motorbase I8, which is in turn guided by and supported on the sub-base I, and the center distance between the driving and driven pulleys may be adjusted by means of the lead screw |9 and the handwheelld. It is of course obvious that the pivoting motor supporting structure of Figures '7 to 9 may also be employed for adjusting the center distance if it is desired.

The multiple belt adjustable diameter pulley 88 is formed by the pulley sections 96 and 91, which are in driving relation to the belt 89, and by the pulley sections 98 and 99 which are in driving relation to the belt 98. The pulley section 88 is axially xed with respect to the pulley section 96 and the pulley section 99 is likewise axially fixed to-the pulley section 91. Thus the effective diameters of the adjustable pulley structures formed by each pair of opposite lacing pulley sections are adjusted by equal increments.

The construction of the multiple belt adjust! able diameter pulley 88 is illustrated in detail by Figure 11. Referring to Figure 11: the driving motor has the motor shaft |8|, which projects from the motor frame and which has sup ported thereon the shaft extension |82. The member |82 is suitably keyed to the motor shaft bythekey |83 and is held against axial movement by the set screw |84. The pulley section 96 is provided with the axially extending hub |05, which is slidably supported on'the shaft extension |82. The pulley section 99 is` provided With the. hub |86, which is slidably supported on the hub |85 by m'eans of bushing |81. Bushing |81 is formed of lubricant retaining material and may be formed in two parts in the same manner as the bushing 33 of Figure 4. Pulley section 91 is provided with the hub |88 which is slidably supported onthe hub |85 by means of the bearing The pulley section 91 is axially xed to the pulley section 99 by means of a plu- V rality ofthreaded rods ||8, which are spaced at equal angular intervals. Each of the rods passes '75 through the pulley sections' 91 and 90 and is threaded into the pulley section 99. Each of the rodsis provided with the flat head and the lock nut ||2, whereby it is secured to the pulley section 91 and is securely fixed in position by means of the set screw H3. The pulley section 98 may be suitably secured to the axially extending hub |05 by means of the set screw H9.`

The driving connection'between the pulley section l96 and the shaft extension |02 is formed by the key- I |5, Figure 12, which engages the member |02 andthe hub |05 of the pulley section. The pulley sections 91, 98 and 99 are in turn rotated together with the pulley section 96 by the y engagement of the key ||6 with the hubs of the pulley sections. Thus the pulley structure is splined to the shaft extension.

It is obvious from the construction of Figures 11 and l2 that the effective diameter 0f the adjustable pulley structure formed by each pair of opposite facingv pulley sections may be adjusted by moving the hub |05 of vthe pulley section 96, and the hub |06 of' the pulley section 99 in op-v posite directions by equal increments. The axial movements of the pulley sections are interlocked by means'of the gears 31 and 30, which respectively engage the racks ||1 and ||0 formed in the hub |05 and the racks ||9 and |20 formed in the hub |06. The gears 31 and 38 are rotatably supported in fixed axial position with respect to the shaft extension |02 by the pin 43, which .passes through the gears and the shaft extension.

The protecting housing 44 of Figures 4 to 6 may again be employed to hold the gears in position and t enclose theinterlocking mechanism. The engagement of the gears 31 and 30 withfthe racks formed in the hubs of the pulley sections interlocks the axial movements of the hubs |05 and |06 in the same manner as in the construction of Figures 4 to 6.

The pulley sections are resiliently urged into driving relation with the belts 89 and 90 by means of 'the spring |00, one end of which engages the` shoulder |2|, formed on the pulley section 99,

and the other end of which engages the cap 48, secured to the hub |05.

It is obvious from the construction that each pair of opposite facing pulley sections are adjusted by equal and opposite increments with respeciI to their respective driving belt and that the effective diameter of the pulley structure formed by the pulley sections 96 and 91 ls always equal t that of the pulley structure formed-'by the pulley sections 98 and 99. It is also obvious that the force engerted by Vthe spring |00 is directly Aengaged by the gear.

v exerted on the pulley sections and that the gears 31 and 38 are required to transmit only the diI'-,

tions having opposed inclined belt engaging faces,

forming by relative axial adjustment variable effective pulley diameters, and means for adjusting the axial positions of said pulley sections by equal and opposite increments comprising, a member pivotally supported about an axis fixed with respect to said shaft and engaging said pair of pulley sections, whereby an axial adjustment of one pulley section results in an equal and opposite axial adjustment of the other pulley section, and 'means supported coaxially with repulley sections toward each other.

2. In an adjustable diameter pulley structure, a shaft, a pulley section having an inclined belt engaging face and a hub slidable on the shaft, another pulley section having an inclined belt engaging face opposed to the inclined face of the other section, as wellas a hub slidable on the hub of the other section, resilient means for'urging the sections, towardeach other, and means for ensuring that the sections will be equally adjusted in an axial direction, comprising a rackand gear mechanism, the gear'having an axis transverse to the shaft and ilxed with respect thereto, the rack having teeth formed in slots in the hubs and engaged by the gear.'

3. In a`n adjustable diameter pulley structure,l

a shaft, a pulley section ha ing an inclined belt engaging face and a hub s idable on the shaft, another pulley section having an inclined belt engaging face opposed to the inclined face of the other section, as well as a hub slidable on the spect to said structure for resiliently urging said aok.

hub of the other section, andmeans for ensur-A ing that the sections will be equallyadjusted in an axial direction, comprising a rack and gear mechanism, the gear having an `axistransver'se to the shaft and `fixed with respect thereto, the l rack having teeth formed in slots in the hubs and VAINO HOOVER. 

